Influence of Underground
Workings and Dump Height on the Stability of Overburden Dumps
Pudari Harish, Inumula Satyanarayana and Karra Ram Chandar
Disaster Advances; Vol. 18(5); 104-113;
doi: https://doi.org/10.25303/185da1040113; (2025)
Abstract
Coal is extracted using both underground and opencast methods of working. During
the coal extraction process, opencast mining produces a significant amount of overburden.
In opencast mines, the removed overburden material is dumped at significant heights
to reduce ground coverage. But overburden dumps with great heights are at risk and
sometimes lead to failure of dumps causing loss of men and machinery. Stability
issues will become more complicated when the overburden is dumped above the old
underground workings. Complication arises because of redistribution of pre-existing
stresses from underground activities affecting the overburden dumps. This study
uses a two-dimensional finite element (FE) analysis program to understand the stability
analysis of overburden dumps above old underground workings. The factor of safety
(FoS) is determined using the strength reduction technique which highlights the
impact of underground excavations on overburden dump stability by highlighting the
required strength reduction factor (SRF).
In order to analyse the overburden dumps with the presence and absence of old underground
workings, numerical models were created for various dump heights. The overburden
dumps with underground workings exhibited SRF values ranging from 1.78 to 2.05,
while the dumps without underground workings had SRF values ranging from 1.81 to
2.55. The displacement of the overburden dump material, which results in 7 mm of
horizontal displacement and 29 mm of vertical displacement, indicates a significant
impact of underground workings on the stability of the overburden dumps. This study
highlights the importance of considering underground workings in the design and
management of overburden dumps to ensure safety and stability.
